Aquatic Environments as Hotspots of Transferable Low-Level Quinolone Resistance and Their Potential Contribution to High-Level Quinolone Resistance

Abstract

The disposal of antibiotics in the aquatic environment favors the selection of bacteria exhibiting antibiotic resistance mechanisms. Quinolones are bactericidal antimicrobials extensively used in both human and animal medicine. Some of the quinolone-resistance mechanisms are encoded by different bacterial genes, whereas others are the result of mutations in the enzymes on which those antibiotics act. The worldwide occurrence of quinolone resistance genes in aquatic environments has been widely reported, particularly in areas impacted by urban discharges. The most commonly reported quinolone resistance gene, qnr, encodes for the Qnr proteins that protect DNA gyrase and topoisomerase IV from quinolone activity. It is important to note that low-level resistance usually constitutes the first step in the development of high-level resistance, because bacteria carrying these genes have an adaptive advantage compared to the highly susceptible bacterial population in environments with low concentrations of this antimicrobial group. In addition, these genes can act additively with chromosomal mutations in the sequences of the target proteins of quinolones leading to high-level quinolone resistance. The occurrence of qnr genes in aquatic environments is most probably caused by the release of bacteria carrying these genes through anthropogenic pollution and maintained by the selective activity of antimicrobial residues discharged into these environments. This increase in the levels of quinolone resistance has consequences both in clinical settings and the wider aquatic environment, where there is an increased exposure risk to the general population, representing a significant threat to the efficacy of quinolone-based human and animal therapies. In this review the potential role of aquatic environments as reservoirs of the qnr genes, their activity in reducing the susceptibility to various quinolones, and the possible ways these genes contribute to the acquisition and spread of high-level resistance to quinolones will be discussed.

Assessing the Microbial Quality of Shrimp (Xiphonaeus kroyeri) and Mussels (Perna perna) Illegally Sold in the Vitória Region, Brazil, and Investigating the Antimicrobial Resistance of Escherichia coli Isolates

“…This environmental contamination, particularly in marine ecosystems, can exert selective pressure on bacterial communities, fostering the development of antibiotic-resistant strains or the proliferation of resistance genes [ 41 ]. The global presence of quinolone resistance genes in aquatic environments has been extensively documented, especially in areas impacted by urban discharges [ 42 ]. In the Vitória Region, there is frequent deposition of untreated effluents directly into the waters where seafood collection often takes place.…”

Occurrence, Bioaccumulation, Metabolism and Ecotoxicity of Fluoroquinolones in the Aquatic Environment: A Review

“…Significant variations in antibiotic concentrations were observed between different countries and regions, with generally higher FQs levels found in surface water from developing countries compared to developed ones. Notably, surface water in India displayed high concentrations of CIP at 542.45 μg/L [ 26 ] and Kenya at 75.70 μg/L [ 16 ]. The Mediterranean waters of Tunisia exhibited elevated levels of ENR (20.70 μg/L) and NOR (40.20 μg/L) [ 27 ].…”

“…Thirdly, discharge from wastewater treatment plants, responsible for handling the treatment of wastewater from urban and industrial areas. However, it is worth noting that complete FQs removal during the treatment process may not always be achieved, resulting in the presence of drug residues in the effluent that can enter the water environment [ 26 , 35 , 37 ]. Gao et al [ 8 ] found that in the Liaohe River Basin in China, the main sources of FQs contamination were wastewater discharge from wastewater treatment plants and agricultural aquaculture.…”

“… a: The comprehensive contamination status of FQs in surface water can be found in Table S2 [ 5 , 6 , 7 , 8 , 9 , 13 , 14 , 15 , 16 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , …”

“…Table S1: Physicochemical properties of selected FQs [ 5 , 6 , 7 , 8 , 9 ]; Table S2. Minimum, maximum, mean, and median concentrations of representative FQs detected in different surface water [ 5 , 6 , 7 , 8 , 9 , 13 , 14 , 15 , 16 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , …”